On Tue, Apr 4, 2017 at 11:27 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 04/04/17 10:47, Thomas Garnier wrote: >> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h >> index 516593e66bd6..12fa851c7fa8 100644 >> --- a/arch/x86/include/asm/pgtable_64_types.h >> +++ b/arch/x86/include/asm/pgtable_64_types.h >> @@ -78,4 +78,15 @@ typedef struct { pteval_t pte; } pte_t; >> >> #define EARLY_DYNAMIC_PAGE_TABLES 64 >> >> +/* >> + * User space process size. 47bits minus one guard page. The guard >> + * page is necessary on Intel CPUs: if a SYSCALL instruction is at >> + * the highest possible canonical userspace address, then that >> + * syscall will enter the kernel with a non-canonical return >> + * address, and SYSRET will explode dangerously. We avoid this >> + * particular problem by preventing anything from being mapped >> + * at the maximum canonical address. >> + */ >> +#define TASK_SIZE_MAX ((_AC(1, UL) << 47) - PAGE_SIZE) >> + >> #endif /* _ASM_X86_PGTABLE_64_DEFS_H */ >> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h >> index 3cada998a402..e80822582d3e 100644 >> --- a/arch/x86/include/asm/processor.h >> +++ b/arch/x86/include/asm/processor.h >> @@ -825,17 +825,6 @@ static inline void spin_lock_prefetch(const void *x) >> #define KSTK_ESP(task) (task_pt_regs(task)->sp) >> >> #else >> -/* >> - * User space process size. 47bits minus one guard page. The guard >> - * page is necessary on Intel CPUs: if a SYSCALL instruction is at >> - * the highest possible canonical userspace address, then that >> - * syscall will enter the kernel with a non-canonical return >> - * address, and SYSRET will explode dangerously. We avoid this >> - * particular problem by preventing anything from being mapped >> - * at the maximum canonical address. >> - */ >> -#define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) >> - >> /* This decides where the kernel will search for a free chunk of vm >> * space during mmap's. >> */ >> > > This should be an entirely separate patch; if nothing else you need to > explain it in the comments. I will explain it in the commit message, it should be easier than a separate patch. > > Also, you say this is for "x86", but I still don't see any code for i386 > whatsoever. Have you verified *all* the i386 and i386-compat paths to > make sure they go via prepare_exit_to_usermode()? [Cc: Andy] I did but I will do it again for the next iteration. > > Finally, I can't really believe I'm the only person for whom "Specific > usage of verity_pre_usermode_state" is completely opaque. I agree, I will improve it. > > -hpa > -- Thomas -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html